1. Field of the Invention
The present invention relates to a latch device, and more particularly to a latch device that is preferable for supporting a backrest of a folding seat such that the backrest is attachable to and detachable from a vehicle body.
2. Description of the Related Art
Conventionally, as a vehicle latch device related to the present invention, there is a latch device shown in FIG. 18. In this conventional latch device, a striker St is restrained by a hook groove Sf formed in a hook F and by a wall surface Fb on a deep side of a base groove Sb into which the striker St formed on a base B enters. With the configuration of this conventional latch device, it is possible to suppress noises generated when the striker St collides against the base groove Sb by vibration caused by running of a vehicle (see, for example, Japanese Patent Application Laid-open No. 2009-57039).
According to the latch device disclosed in Japanese Patent Application Laid-open No. 2009-57039, as shown in FIGS. 18 and 19, the wall surface Fb of the base groove Sb is inclined at an angle θ2 with respect to a direction X that is perpendicular to an entering direction Y where the striker St enters into the base groove Sb, and the wall surface Fb is formed into a convex shape. Further, the hook F is formed into a convex shape, and a restraint surface Fc of the hook groove Sf that restrains the striker St together with the wall surface Fb is inclined at an angle θ3 (<θ2) with respect to the direction X.
Accordingly, the striker St is restrained by the wall surface Fb and the restraint surface Fc at a stable position Ps of a portion of the wall surface Fb projecting upward in FIGS. 18 and 19 and of a portion of the restraint surface Fc projecting upward in these drawings.
When the latch device described in Japanese Patent Application Laid-open No. 2009-57039 is mounted on a backrest of a folding seat and is used, if the vehicle is suddenly decelerated or has a collision, an impact force in a releasing direction is applied from the striker St to the hook F in a direction opposite from the entering direction Y. The hook F is rotated by this impact force in a counterclockwise direction shown with an arrow Af in FIG. 18. At the same time, because the restraint surface Fc projects upward as shown in FIG. 19, responses with respect to the applied impact force are fluctuated, and the striker St tends to move rightward or leftward shown with arrows in FIG. 19 along the restraint surface Fc.
Therefore, in the latch device described in Japanese Patent Application Laid-open No. 2009-57039, the striker St moves to various positions in the hook groove Sf by the applied impact force and thus its moving direction is unstable. Therefore, according to the latch device of Japanese Patent Application Laid-open No. 2009-57039, even if applied impact forces have the same magnitude, because the distance between the hook F and the striker St differs depending on a moving position of the striker St in the hook groove Sf, there is a possibility that the strength of the latch device is fluctuated.